So when it games to games based on the old Unreal engine there are two main choices of renderes to use are: The enhanced Opengl which you can find here http://www.cwdohnal.com/utglr/
and Kentie's Direct X 10 plugin. http://kentie.net/indices/2.htm

Which one do you use and why?

if you have nvidia, best use dx9 or openGL, because you can then force highest quality antialiasing that's not supported by dx10.

Exactly as GanjaStar said. But if you still want to go with the updated drivers then go with the DirectX one. OpenGL is slower though it doesn't matter in the case of these games. There is no chance for a single slowdown anyway.